Threaded insert for fasteners

ABSTRACT

A threaded insert for providing stronger threads to a parent material. The threaded insert includes a bushing portion having male threads on the external surface and female threads within an internal bore. The threaded insert also includes keys which lock the threaded insert into a threaded hole within the parent material. The keys are positioned within slots along the external surface of the bushing portion of the threaded insert. The slots include two substantially parallel walls which are substantially perpendicular to a bottom surface of the slots. A method for assembling the threaded insert reduces the tendency of the keys to be installed offset from the bottom surface of the slots.

RELATED APPLICATIONS

This is a continuation of Ser. No. 10/716,569, filed Nov. 18, 2003, nowU.S. Pat. No. 6,969,221, which is a continuation of Ser. No. 10/153,167,filed May 22, 2002, now U.S. Pat. No. 6,672,811.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to threaded inserts, and moreparticularly to a threaded insert having keys which are positionedwithin 90° straight wall slots.

2. Description of the Related Art

Threaded inserts of the type to which this invention is directed areordinarily used to provide strong, permanent threads in soft or ductileparent materials, especially when a mating stud or bolt is to befrequently removed. Threaded inserts are also used to repair stripped,damaged or worn threads in a parent material. Soft or ductile materialswhich have received threaded inserts typically exhibit improvedload-carrying capacity under static and dynamic loading conditions.

Referring to FIGS. 1 a, 1 b and 1 c, a prior art threaded insertincludes a bushing portion having a cylindrical shape with a centralbore throughout the length of the threaded insert. The bushing portionalso includes female threads throughout the length of the surface withinthe central bore and male threads throughout the length of the externalsurface of the bushing portion. The male threads on the external surfaceof the bushing portion are configured to mate with a threaded holewithin a parent material, such as a plate or casting made of aluminum ormagnesium. The female threads within the central bore are configured tomate with a male threaded fastener, such as a bolt or stud. The threadedinsert is typically made from a material which is stronger than theparent material, such as steel.

To ensure that the prior art threaded insert does not rotate within thethreaded hole in the parent material when a male threaded fastener isbeing installed or removed, the threaded insert includes at least onekey. The at least one key is ordinarily positioned within a dovetailslot which extends longitudinally along the external.

The dovetail slot is added to the threaded insert through a broachingoperation. The broaching operation includes forcing an elongated,serrated cutting tool having sequentially larger teeth in the form ofthe dovetail slot along the external surface of the threaded insert.During manufacturing of the threaded fastener, the broaching stepgenerally requires an additional machine set-up, which can lead toincreased manufacturing costs. Also, broaching tools are oftenrelatively expensive compared to other types of tools, thus addingfurther to the manufacturing costs of the threaded insert.

After the broaching operation, the dovetail slot is deburred to removeany protruding ragged edges that may have been raised on the malethreads on the external surface of the threaded insert during thebroaching operation. The deburring operation is often performed by hand,which can add to the time and cost required to fabricate the threadedinsert.

The key includes a tang portion and a locking portion with the tangportion and the locking portion being positioned adjacent each other andaligned longitudinally. A cross section of the tang portion includes asubstantially rectangular shape, while a cross section of the lockingportion includes a substantially triangular shape. The tang portion ispositioned within the dovetail slot through an interference fit. Aninside surface on the tang portion is preferably in contact with thebottom surface of the dovetail slot and the outside facing edges of thetang portion are broached into the angled surfaces of the dovetail slot.The thickness of the tang portion is sufficiently low that with the tangportion being in contact with the bottom surface of the dovetail slot,the outer corners of the tang portion remain deeper than the insidediameter of the male threads on the external surface of the threadedinsert. This prevents the tang portion from interfering with the threadswithin the hole in the parent material during installation of thethreaded insert. Prior to installation of the threaded insert into theparent material, the locking portion is positioned beyond the end of thebushing portion of the threaded insert. The thickness of the lockingportion is sufficient that the outermost portion of the locking portionis positioned substantially flush with the outside diameter of the malethreads on the external surface of the threaded insert.

During installation of the key into the dovetail slot, the insidesurface of the tang portion of the key is substantially aligned with thebottom surface of the dovetail slot at an end of the threaded insert. Alongitudinal force is applied to the key so that the tang portion of thekey is pushed into the dovetail slot with the outside edges of the tangportion being broached into the angled surfaces of the dovetail slot.With no positive forces pushing the tang portion against the bottomsurface of the dovetail slot during installation of the key into thedovetail slot, the inside surface of the tang portion may inadvertentlybe installed offset from the bottom surface of the dovetail slot.Therefore, a key resetting operation is performed to ensure that thetang portion is not positioned within the male threads on the externalsurface of the threaded insert. The key resetting operation includesapplying a force to the tang portion of the key in a directionsubstantially perpendicular to the bottom surface of the dovetail slot.For those keys which are located with the tang portion offset from thebottom surface of the dovetail slot, the key resetting operation maycause the key to be pushed out of the newly broached portion of theangled surfaces of the slot and to become loose, which may be asufficient reason to scrap the threaded insert. Also, the key resettingoperation is a process which increases the manufacturing cost of thethreaded insert.

At installation, the threaded insert may be screwed into the threadedhole in the parent material until the locking portion of the at leastone key on the threaded insert contacts a surface of the parentmaterial. The at least one key is then driven into the parent materialso that the locking portion of the key broaches through the threads ofthe threaded hole in the parent material and remains in place within thethreads in the parent material. Having the key in place within thethreads in the parent material locks the threaded insert in place bypreventing further rotation of the threaded insert within the threadedhole in the parent material. While driving the at least one key into theparent material, the tang portion of the key is simultaneously broachedfurther into the angled surfaces of the dovetail slot, thereby adding tothe difficulty of driving the key into the parent material.

In light of the foregoing description, those skilled in the art haverecognized the need for a threaded insert having at least one lockingkey but having less tendency to broach into the slot within the threadedinsert. The need for a threaded insert which can be manufactured moreeconomically and with improved retention and alignment of the keys hasalso been recognized. Further, the need for a threaded insert which isconfigured for improved key driving has been recognized. The presentinvention fulfils these needs and others.

SUMMARY OF THE INVENTION

Briefly, and in general terms, the present invention is directed to athreaded insert having keys which are positioned within slots havingsubstantially parallel walls that are substantially perpendicular to thebottom surface of the slot.

In a currently preferred embodiment of the invention, the threadedinsert includes at least one key. While those skilled in the art willrecognize that more than one key and slot may be provided within thescope of the invention, reference will be made to an embodiment whereinonly one key, slot and related surfaces are described. The key includesa substantially longitudinal tang portion having a first end, a secondend, a first face, a second face, a first side surface and a second sidesurface. The first face and the second face are substantially paralleland have a curved profile, the first face having a concave surface andthe second face having a convex surface. The first and second sidesurfaces are adjacent to the first face and the second face.

The key also includes a substantially longitudinal locking portionhaving a first end, a second end and a substantially triangular crosssection which forms a back face and two angled faces. The second end ofthe locking portion is positioned adjacent the first end of the tangportion such that the tang portion and the locking portion aresubstantially longitudinally aligned. The back face is substantiallylongitudinally aligned with an apex of the first surface of the tangportion, while the intersection of the two-angled faces project beyondan apex of the second surface of the tang portion.

In another currently preferred aspect of the invention, the threadedinsert also includes a bushing portion. The bushing portion includes asubstantially cylindrical shape with a first end, a second end and acentral bore therethrough. A surface of the central bore includes femalethreads throughout the length of the bushing portion, while an externalsurface of the bushing portion includes male threads throughout thelength of the bushing portion. The bushing portion also includes atleast one slot which is positioned on the external surface and extendssubstantially longitudinally throughout the length of the bushingportion. The slot includes a bottom surface and two wall surfaces. Thetwo wall surfaces are substantially parallel to each other andsubstantially perpendicular to the bottom surface with the depth of theslot being greater than the depth of the male threads on the externalsurface.

In a further currently preferred aspect of the invention, the tangportion of the key is positioned within the slot toward the first end ofthe bushing portion. The edges between the first face and the first andsecond side surfaces of the tang portion are positioned in contact withthe bottom surface of the slot in the bushing portion. The edges betweenthe second face and the first and second side surfaces of the tangportion have an interference fit with the two walls within the slot ofthe bushing portion. The locking portion of the key extends beyond thefirst end of the bushing portion. The depth of the slot of the bushingportion is sufficient that the apex of the second surface of the tangportion of the prior art key is positioned at a depth which is deeperthan the inside diameter of the male threads on the external surface ofthe bushing portion. The depth of the slot of the bushing portion alsoplaces the intersection of the two angled faces of the locking portionof the corresponding key at a depth which is shallower than the insidediameter of the male threads on the external surface of the bushingportion.

In a currently preferred detailed aspect of the invention, the malethreads on the external surface of the bushing portion are configured tomate with a threaded hole in a parent material, while the female threadswithin the central bore are configured to mate with a male threadedfastener. In another currently preferred aspect of the invention, thekey includes four keys which are positioned approximately ninety degreesapart from each other about the circumference of the bushing portion.The first and second side surfaces of the tang portion of the key aresubstantially perpendicular to tangents along the first face of the tangportion at the intersection of the first face and the first and secondsides respectively. The angled faces of the locking portion of the keytaper into the second face of the tang portion of the key. In onecurrently preferred aspect of the invention, the taper includes anangled taper, while in another currently preferred aspect of theinvention the taper includes a curved taper. In a further currentlypreferred aspect of the invention, the intersection of the angled facesof the locking portion of the key may be positioned either above flush,below flush or substantially flush with the outside diameter of the malethreads on the external surface of the bushing portion. The lockingportion of the key further includes an end surface at the first end ofthe locking portion. The end surface is substantially perpendicular tothe back face and the two angled faces of the locking portion. In anadditional currently preferred aspect of the invention, the entirelocking portion of the key extends beyond the first end of the bushingportion. In another currently preferred aspect of the invention, thefirst side surface and the second side surface of the tang portion ofthe key have an interference fit with the two walls within the slot ofthe bushing portion.

The invention also includes a currently preferred method of assemblingthe threaded insert. The method includes providing the key and thebushing portion. The method also includes positioning the tang portionof the key within the slot toward the first end of the bushing portionsuch that the edges between the first face of the tang portion and thefirst and second side surfaces of the tang portion are in contact withthe bottom surface of the slot in the bushing portion. The tang portionis also positioned such that the locking portion of the key extendsbeyond the first end of the bushing portion. The method further includesapplying a force to the second face of the tang portion of the key in adirection substantially perpendicular to the bottom surface of the slot.The force is applied until the curved profile of the tang portion of thekey is reduced and an apex of the second face of the tang portion ispositioned at a depth which is deeper than the inside diameter of theexternal threads of the bushing portion. The force is also applied untilan interference fit is formed between the tang portion of the key andthe slot of the bushing portion.

In a detailed aspect of the currently preferred method of assembling thethreaded insert, applying a force to the second face of the tang portionincludes applying the force until the interference fit is formed betweenthe walls of the slot of the bushing portion and the edges between thesecond face and the first and second sides of the tang portion of thekey. In another currently preferred detailed aspect of the invention,applying a force to the second face of the tang portion includesapplying the force until the interference fit is formed between thewalls of the slot of the bushing portion and the first and second sidesurfaces of the tang portion of the key.

From the above, it may be seen that the invention provides for athreaded insert having at least one key which is positioned within aslot having parallel walls that are perpendicular to the bottom surfaceof the slot. It may also be seen that the key has less tendency tobroach into the slot within the bushing portion and that the threadedinsert is configured for improved key driving compared to prior artthreaded inserts. Additionally, it may be seen that the threaded insertof the invention can be manufactured more economically and with improvedretention and alignment of the key compared to prior art threadedinserts. These and other aspects and advantages of the invention willbecome apparent from the following detailed description and theaccompanying drawings, which illustrate by way of example the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is an elevation view, partly in cross section, depicting aprior art threaded insert.

FIG. 1 b is a plan view of the prior art threaded insert of FIG. 1 ataken from line 1 b—1 b in FIG. 1 a.

FIG. 1 c is a section view depicting a portion of the prior art threadedinsert of FIG. 1 a taken from line 1 c in FIG. 1 b.

FIG. 2 is a perspective view depicting a threaded insert of the presentinvention.

FIG. 3 a is an elevation view depicting a key of the threaded insert ofFIG. 2.

FIG. 3 b is an elevation view depicting the key of FIG. 3 a taken fromline 3 b—3 b in FIG. 3 a.

FIG. 4 a is an elevation view, partly in cross section, depicting thethreaded insert of FIG. 2.

FIG. 4 b is a plan view of the threaded insert of FIG. 2 taken from line4 b—4 b in FIG. 4 a.

FIG. 4 c is a section view depicting a portion of the threaded insert ofFIG. 4 a taken from line 4 c in FIG. 4 b.

FIG. 5 a is a section view depicting a portion of the installation ofthe threaded insert of FIG. 2.

FIG. 5 b is a section view depicting a portion of the installation ofthe threaded insert of FIG. 2.

FIG. 6 is a perspective view depicting an installation tool forfacilitating the installation of the threaded insert of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings, which are provided for purposes ofillustration, but not by the way of limitation, the invention isembodied in a threaded insert which is used to provide strong, permanentthreads in a relatively soft or ductile parent material. Referring tothe drawings in which like reference numerals are used to designate likeor corresponding elements among the figures, FIG. 2 depicts a threadedinsert 20 of the present invention. The threaded insert 20 includes abushing portion 22 having a substantially cylindrical shape with a firstend 24, a second end 26 and a central bore 28 therethrough. A surface ofthe central bore 28 includes female threads 30 throughout the length ofthe bushing portion 22, while an external surface 32 of the bushingportion includes male threads 34 throughout the length of the bushingportion. The male threads 34 may be configured to mate with a threadedhole 36 (FIGS. 5 a and 5 b) in a parent material 38, such as a plate orcasting, while the female threads 30 may be configured to mate with amale threaded fastener, such as a bolt or a stud (not shown). Thethreaded insert 20 also includes at least one key 40 for ensuring thatthe threaded insert does not rotate within the threaded hole in theparent material after installation into the parent material. Each of thekeys 40 is positioned within a slot 42 which extends substantiallylongitudinally along the external surface 32 of the bushing portion 22.In one currently preferred embodiment, the threaded insert 20 includesfour keys 40 which are positioned within four respective slots arrangedapproximately ninety degrees apart from each other about thecircumference of the bushing portion 22.

Referring to FIGS. 3 a and 3 b, the key 40 includes a tang portion 44and a locking portion 46 which may be formed from a single piece ofmaterial which is stronger than the parent material. The tang portion 44may include a substantially longitudinal structure having a first end47, a second end 49, a first face 48 and a second face 50. The firstface 48 and the second face 50 of the tang portion 44 may besubstantially parallel and include a curved profile with the first faceforming an inside, concave curved surface and the second face forming anoutside, convex curved surface. The tang portion 44 may also include afirst side surface 52 and a second side surface 54. The first sidesurface 52 may be substantially perpendicular to the tangent along thefirst face 48 at the intersection of the first face and the first sidesurface. Similarly, the second side surface 54 may be substantiallyperpendicular to the tangent along the first face 48 at the intersectionof the first face and the second side surface. The curved shape of thetang portion 44 may be created through manufacturing processes which arewell known in the art, such as stamping.

The locking portion 46 of the key 40 may include a substantiallylongitudinal structure which is positioned adjacent to the tang portion44. The locking portion 46 may include a first end 55, a second end 57and a substantially triangular cross section. The triangular crosssection may include a back face 56 and two angled faces 58. The secondend 57 of the locking portion 46 may be positioned adjacent to the firstend 47 of the tang portion 44 such that the tang portion and the lockingportion are substantially longitudinally aligned. The back face 56 ofthe locking portion 46 may be substantially longitudinally aligned withan apex 60 of the first face 48 of the tang portion 44. The two angledfaces 58 of the locking portion 46 may taper into the second face 50 ofthe tang portion 44 of the key 40, such as through an angled taper or acurved taper. The distance between the back face 56 and the intersection62 between the two angled faces 58 is sufficient such that afterinstallation of the key 40 into the slot 42 in the bushing portion 22(FIGS. 4 a, 4 b and 4 c), the intersection of the angled faces ispositioned at a depth which is shallower than the inside diameter 72 ofthe male threads 34 on the external surface 32 of the bushing portion.In one currently preferred embodiment, the intersection 62 of the twoangled faces 58 of the locking portion 46 may be positionedsubstantially flush with the outside diameter 64 of the male threads 34on the external surface 32 of the bushing portion 22. In other currentlypreferred embodiments, the intersection 62 of the two angled faces 58 ofthe locking portion 46 may be positioned either above flush or belowflush with the outside diameter 64 of the male threads 34 on theexternal surface 32 of the bushing portion 22. An end surface 66 at thefirst end 55 of the locking portion 46 may be substantiallyperpendicular to the back face 56 and the two angled faces 58.

Referring to FIGS. 4 a, 4 b and 4 c, each of the slots 42 in the bushingportion 22 of the threaded insert 20 includes a bottom surface 68 andtwo walls 70 which are substantially perpendicular to the bottomsurface. The width of each slot 42 is sufficient to accommodate the tangportion 44 and the locking portion 46 of a key 40. The depth of eachslot 42 is greater than the depth of the male threads 34 on the externalsurface 32 of the bushing portion 22 and is sufficiently deep that withthe key 40 installed in the bushing portion, the tang portion 44 of thekey remains at a depth which is deeper than the inside diameter 72 ofthe male threads of the bushing portion.

The bushing portion 22 of the threaded insert 20 may be fabricatedthrough manufacturing techniques which are well known in the art. Forexample, the bushing portion 22 may be manufactured from round bar stockon a computer numerical control (CNC) machine (not shown). A CNC machinemay machine the female threads 30 within the central bore 28 and themale threads 34 on the external surface 32 in a single machine setup.With the same machine setup, the slots 42 may be machined. With theslots 42 including the two walls 70 which are perpendicular to thebottom surface 68 of the slots, the slots may be produced through theuse of a simple tool, such as a circular saw or a milling cutter. Thecost for a machine tool such as a circular saw blade or a milling cutteris considerably less than the cost for a broaching tool such as thoseused to produce the slots of prior art configurations.

Producing the slots 42 with a circular saw creates fewer burrs on themale threads 34 than the broaching method used to produce the slots ofprior art configurations, thereby reducing the time and cost requiredfor deburring. Also, the deburring step may be automated and performedby the CNC machine with the same machine setup as for machining thefemale threads 30, male threads 34 and slots 42, thereby furtherreducing the time and cost required to fabricate the bushing portion 22.After machining the female threads 30, male threads 34 and slots 42, anddeburring the slots on the CNC machine, the bushing portion 22 of thethreaded insert 20 may be cut off from the round bar stock to a finishedlength.

In assembling the threaded insert 20, the tang portion 44 of each of thekeys 40 may be inserted into a corresponding slot 42 toward the firstend 24 of the bushing portion 22 such that the edge 74 (FIGS. 3 a and 3b) of the tang portion between the first face 48 and the first sidesurface 52 and the edge 76 (FIGS. 3 a and 3 b) between the first faceand the second side surface 54 are in contact with the bottom surface 68of the slot. The locking portion 46 of each of the keys 40 may extendbeyond the first end 24 of the bushing portion 22 during the assemblyprocess. In one currently preferred embodiment, the entire lockingportion 46 of each of the keys 40 extends beyond the first end 24 of thebushing portion 22.

To retain the keys 40 within their respective slots 42, a force may beapplied to the second face 50 of the tang portion 44 of each key in adirection substantially perpendicular to the bottom surface 68 of thecorresponding slot in order to reduce the curved profile of the tangportion. Reducing the curved profile of the tang portion 44 causes thefirst 52 and second 54 side surfaces (FIGS. 3 a and 3 b) of the tangportion to spread apart, resulting in the edges 78, 80 of the tangportion 44 between the second face 50 and the first 52 and second 54side surfaces contacting the two walls 70 of the slot 42 and creating aninterference fit between the tang portion and the slot. Alternatively,the first 52 and second 54 side surfaces of the tang portion 44 maycontact the two walls 70 of the slot 42 and create an interferencebetween the tang portion and the slot.

The assembly process facilitates positioning of the tang portion 44 ofthe keys 40 in contact with the bottom surface 68 of the slot 42. Withthe edges 74, 76 between the first face 48 and the first 52 and second54 side surfaces of the tang portion 44 positioned in contact with thebottom surface 68 of the slot 42, there is less need for a key resettingprocess as performed on threaded inserts of prior art configurations. Byreducing the need of the key resetting process from the assembly of thethreaded insert 20, the production cost of the threaded insert isreduced. Also, positioning the edges 74, 76 between the first face 48and the first 52 and second 54 side surfaces of the tang portion 44 ofthe keys in contact with the bottom surface 68 of the slots 42 improvesthe alignment of the keys 40 with the slots and increases the retentionof the keys within the slots, thereby reducing the amount of scrapcreated during the assembly of the threaded inserts 20 compared to priorart threaded insert configurations.

Referring to FIG. 5 a, installation of the threaded insert 20 into theparent material 38 includes aligning the second end 26 of the bushingportion 22 of the threaded insert with the threaded hole 36 in theparent material and screwing the threaded insert into the threaded holewithin the parent material. In one currently preferred embodiment, thethreaded insert 20 is screwed into the parent material 38 until thefirst end 24 of the bushing portion 22 is approximately 0.25–0.76 mm(0.01–0.03 inches) below the surface 82 of the parent material. Thedepth to which the threaded insert 20 is screwed into the threaded hole36 in the parent material 38 may be controlled by the longitudinalplacement of the locking portion 46 of the keys 40 during assembly ofthe threaded insert. Since the locking portion 46 of the keys 40 extendsinto the male threads 34 on the external surface 32 of the bushingportion 22 of the threaded insert 20, the threaded insert can only bescrewed into the threaded hole 36 within the parent material 38 untilthe locking portion of the keys contacts the parent material. In thismanner, the locking portion 46 of the keys 40 may act as a depth-controlstop for the threaded insert 20.

As shown in FIG. 5 b, with the threaded insert 20 positioned at adesired depth within the threaded hole 36 in the parent material 38, thekeys 40 may be driven into the threads 84 within the hole in the parentmaterial. The process of driving the keys 40 into the threads 84 withinthe hole 36 in the parent material 38 causes the locking portion 46 ofthe keys to broach through the threads of the hole in the parentmaterial. The keys 40 may remain in place within the newly broachedportion of the threads 84 of the parent material 38, thereby locking thethreaded insert 20 in place and preventing the threaded insert fromrotating during installation or removal of male threaded fasteners intothe female threads 30 (FIG. 2) within the central bore 28 of the bushingportion 22. The keys 40 may be driven into the threads within the holein the parent material through the application of several light tapsfrom a tool, such as a hammer or a mallet, directly onto the endsurfaces 66 at the first end 55 of the locking portion 46 of the keys.The keys 40 may be driven until the end surfaces 66 at the first end 55of the locking portion 46 of the keys are substantially flush, or belowflush, with the surface 82 of the parent material 38.

Alternatively, the keys 40 may be driven into the threads within thehole 36 in the parent material 38 through the use of an installationtool 86 (FIG. 6) which may include a substantially longitudinal,cylindrical shaft 88. In one currently preferred embodiment, theinstallation tool 86 may include at least a first cylindrical portion 90and a second cylindrical portion 92 which are substantiallylongitudinally aligned about the longitudinal axis 94 of the cylindricalshaft 88.

The first cylindrical portion 90 is positioned at a first end 96 of theinstallation tool 86. The first cylindrical portion 90 may include afirst diameter 98 which is slightly smaller than the inside diameter 100of the female threads 30 within the central bore 28 of the bushingportion 22 of the threaded insert 20 (FIGS. 4 a and 4 b). The firstcylindrical portion 90 may also include a first length which is greaterthan the distance by which the locking portion 46 of the keys 40 in thethreaded insert 20 extend from the first end 24 of the bushing portion22 of the threaded insert (FIGS. 4 a and 4 b).

The second cylindrical portion 92 may include a first face 102 which maybe positioned adjacent to the first cylindrical portion 90 and a secondface 104 on the opposite end of the second cylindrical portion. Thesecond cylindrical portion 92 may include a second diameter 106 which islarger than the first diameter 98 of the first cylindrical portion 90such that the first face 102 is sufficiently large to contact the endsurfaces 66 at the first end 55 of the locking portion 46 of each of thekeys 40 (FIG. 2) within the threaded insert 20 simultaneously.

To drive the keys 40 through the use of the installation tool 86, thefirst cylindrical portion 90 may be inserted into the central bore 20(FIGS. 4 a and 4 b) from the first end 24 of the bushing portion 22 ofthe threaded insert 20 until the first face 102 on the secondcylindrical portion 92 contacts the end surfaces 66 at the first end 55of the locking portion 46 of the keys 40. The keys 40 may then be driventhrough the application of several light taps on the second face 104 ofthe second cylindrical portion 92 of the installation tool.

As a result of the configurations of the slots 42 and the tang portion44 of the keys 40, and the method of assembling the keys with thebushing portion 22, the tendency of the keys to broach into the walls 70of the slots is reduced compared to threaded inserts of prior artconfigurations. Further, the tendency of the keys 40 to broach into thewalls 70 of the slots 42 through the driving of the keys duringinstallation of the threaded insert 20 into the threaded hole 36 in theparent material 38 is reduced compared to threaded inserts of prior artconfigurations. Therefore, the keys 40 are more easily driven into theparent material 38 during installation of the threaded insert 20 of thepresent invention than are the keys in threaded inserts of prior artconfigurations.

From the foregoing, it will be apparent to those skilled in the art offastener designs that while particular forms of the invention have beenillustrated and described, various modifications can be made withoutdeparting from the spirit and scope of the invention. Accordingly, it isnot intended that the invention be limited, except as by the appendedclaims.

1. A key for a threaded insert, the threaded insert having asubstantially cylindrical bushing portion with a threaded central boretherethrough, a radially outside surface of the bushing portionincluding male threads throughout the length of the bushing portion andat least one slot extending substantially longitudinally throughout thelength of the bushing portion for receiving the key, the key comprising:a substantially longitudinal locking portion connected to asubstantially longitudinal tang portion, the substantially longitudinaltang portion including a first end, a second end, a radially insideface, a radially outside face, a first side surface and a second sidesurface, the radially inside face and the radially outside face of thesubstantially longitudinal tang portion being substantially parallel andhaving a curved profile with a preset curvature, wherein the radiallyinside face has a concave surface, and the radially outside face has aconvex surface, the substantially longitudinal locking portion includinga first end and a second end, and the substantially longitudinal lockingportion having a substantially triangular cross section, the triangularcross section forming a back face and two angled faces, and wherein atthe second end of the locking portion the angled faces of the lockingportion of the key taper into the radially outside face of the tangportion of the key, and the back face of the triangular cross section issubstantially aligned with an apex of the concave surface of theradially inside face of the substantially longitudinal tang portion, andwhereby reduction of said curvature of said curved profile is operativeto spread said first and second side edges apart to engage said at leastone slot and to create an interference fit between said tang portion andsaid at least one slot.
 2. The key of claim 1, wherein: the first sidesurface of the tang portion of the key is substantially perpendicular toa tangent along the radially inside face of the tang portion at theintersection of the first side surface and the radially inside face; andthe second side surface of the tang portion of the key is substantiallyperpendicular to a tangent along the radially inside face of the tangportion at the intersection of the second side surface and the radiallyinside face.
 3. The key of claim 1, wherein the taper includes an angledtaper.
 4. The key of claim 1, wherein the taper includes a curved taper.5. The key of claim 1, further comprising an end surface at the firstend of the locking portion of the key, the end surface beingsubstantially perpendicular to the back face and the two angled faces ofthe locking portion.